Autonomous robot charging profile selection

ABSTRACT

An electrical charging station for charging an autonomous robot having a battery. The charging station includes a first charging member configured to receive a second charging member on the autonomous robot when the autonomous robot is docked with the charging station. There is a communications device configured to receive from the autonomous robot an identifier indicative of a type of battery on the autonomous robot. There is a power supply, electrically connected to the first charging member, configured to charge the autonomous robot according to a charging profile. The charging profile is selected based at least in part on the identifier received from the autonomous robot.

FIELD OF THE INVENTION

This invention relates to an electrical charging system and moreparticularly to such a system which automatically selects a chargingprofile for an autonomous robot.

BACKGROUND OF THE INVENTION

In many applications, robots are used to perform functions in place ofhumans or to assist humans in order to increase productivity andefficiency. One such application is order fulfillment, which istypically performed in a large warehouse filled with products to beshipped to customers who have placed their orders over the internet forhome delivery.

Fulfilling such orders in a timely, accurate and efficient manner islogistically challenging to say the least. Clicking the “check out”button in a virtual shopping cart creates an “order.” The order includesa listing of items that are to be shipped to a particular address. Theprocess of “fulfillment” involves physically taking or “picking” theseitems from a large warehouse, packing them, and shipping them to thedesignated address. An important goal of the order-fulfillment processis thus to ship as many items in as short a time as possible. Inaddition, the products that will ultimately be shipped first need to bereceived in the warehouse and stored or “placed” in storage bins in anorderly fashion throughout the warehouse so they can be readilyretrieved for shipping.

Using robots to perform picking and placing functions may be done by therobot alone or with the assistance of human operators. The robots arepowered by electricity, which is stored in batteries onboard the robot.With all of the travelling that the robots do around the warehouse theymust be regularly recharged. Therefore, for the operation to runsmoothly, an efficient and effective way to charge the robots is arequirement.

BRIEF SUMMARY OF THE INVENTION

The benefits and advantages of the present invention over existingsystems will be readily apparent from the Brief Summary of the Inventionand Detailed Description to follow. One skilled in the art willappreciate that the present teachings can be practiced with embodimentsother than those summarized or disclosed below.

In one aspect, the invention includes an electrical charging station forcharging an autonomous robot having a battery. There is a first chargingmember on the electrical charging station configured to receive a secondcharging member on the autonomous robot when the autonomous robot isdocked with the charging station for charging. There is a communicationsdevice configured to receive from the autonomous robot an identifierindicative of a type of battery on the autonomous robot. There is also apower supply, electrically connected to the first charging member,configured to charge the autonomous robot according to a chargingprofile. The charging profile is selected based at least in part on theidentifier received from the autonomous robot.

In other aspects of the invention, one or more of the following featuresmay be included. The identifier may comprise one or more of a batterytype, an autonomous robot type, or battery condition. The batterycondition may include a battery temperature and for a certain batterytype the charging profile for a normal battery temperature range may bedifferent than the charging profile for either a battery temperatureabove the normal temperature range or below the normal temperaturerange. The charging station may include a memory for storing a pluralityof charging profiles, at least one of which corresponds to theidentifier. The communications device may include a transceiver forcommunicating with a corresponding transceiver on the autonomous robot.The transceiver of the charging station and the correspondingtransceiver on the autonomous robot may be optical transceivers and maycommunicate using an IrDA communications protocol. There may further beincluded a current sensor configured to sense a current output from thepower supply to the autonomous robot and a voltage sensor configured tosense a voltage across the first charging member applied by the powersupply. There may also be included a processor configured to control thepower supply to charge the autonomous robot according to the chargingprofile and the charging profile may include a constant current portionand a constant voltage portion. The processor may be configured tocharge the robot in the constant current charging portion of thecharging profile using a constant current until a predetermined voltagelevel is reached and to then charge the robot in the constant voltageportion of the charging profile using a constant voltage. During theconstant voltage charging portion of the charging profile the processormay be configured to provide the SOC to the robot and terminate chargingwhen a SOC request from the robot has been received indicating an upperbattery voltage threshold has been reached or when a predeterminedcurrent level is being output by the power supply, in both casesindicating a fully charged battery. The processor may be configured tocontrol the power supply after the robot is fully charged but before therobot has undocked from the charging station to charge the robot using afloat charging profile which provides a limited charge level to therobot by maintaining a constant voltage level until the robot isundocked. The processor may be configured to charge the robot in a deadbattery state using a recovery profile having a constant current portionand a constant voltage portion and the processor may be furtherconfigured to prompt a user to start the robot upon completion of therecovery charging profile so that communication between the robot andthe charging station can be established to complete robot charging usinga charging profile selected based at least in part on the identifierreceived from the autonomous robot.

In another aspect, the invention includes a method for charging anautonomous robot having a battery. The method includes docking anautonomous robot by mating a first charging member on an electricalcharging station with a second charging member on the autonomous robot.The method also includes receiving a communication from the autonomousrobot having an identifier indicative of a type of battery on theautonomous robot. The method further includes charging, using a powersupply, the autonomous robot according to a charging profile. Thecharging profile is selected based at least in part on the identifierreceived from the autonomous robot.

In yet other aspects of the invention, one or more of the followingfeatures may be included The identifier may comprise one or more of abattery type, an autonomous robot type, or battery condition. Thebattery condition may include a battery temperature and for a certainbattery type the charging profile for a normal battery temperature rangemay be different than the charging profile for either a batterytemperature above the normal temperature range or below the normaltemperature range. The method may further include storing in a memory inthe charging station a plurality of charging profiles, at least one ofwhich corresponds to the identifier. The receiving step may includecommunicating with optical transceivers one on each of the autonomousrobot and on the charging station and it may include using an IrDAcommunications protocol. The method may further include sensing acurrent output from the power supply to the autonomous robot using acurrent sensor and sensing a voltage across the first charging memberapplied by the power supply using a voltage sensor. The method may alsoinclude controlling the power supply to charge the autonomous robotaccording to the charging profile and the charging profile may include aconstant current portion and a constant voltage portion. The method mayfurther include charging the robot in the constant current chargingportion of the charging profile using a constant current until apredetermined voltage level is reached and charging the robot in theconstant voltage portion of the charging profile using a constantvoltage until a predetermined current level is reached. During theconstant voltage charging portion of the charging profile the method mayinclude providing the SOC to the robot and terminating charging when aSOC request from the robot has been received indicating an upper batteryvoltage threshold has been reached or when a predetermined current levelis being output by the power supply, in both cases indicating a fullycharged battery. The method may include controlling the power supplyafter the robot is fully charged but before the robot has undocked fromthe charging station to charge the robot using a float charging profilewhich provides a limited charge level to the robot by maintaining aconstant voltage level until the robot is undocked. The method mayadditionally include charging the robot in a dead battery state using arecovery profile having a constant current portion and a constantvoltage portion, and prompting a user to start the robot upon completionof the recovery charging profile so that communication between the robotand the charging station can be established to complete robot chargingusing a charging profile selected based at least in part on theidentifier received from the autonomous robot.

These and other features of the invention will be apparent from thefollowing detailed description and the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the present invention will now be described, by way ofexample only, with reference to the attached Figures, wherein:

FIG. 1 is a top plan view of an order-fulfillment warehouse;

FIG. 2A is a front elevational view of a base of one of the robots usedin the warehouse shown in FIG. 1;

FIG. 2B is a perspective view of a base of one of the robots used in thewarehouse shown in FIG. 1;

FIG. 3 is a perspective view of the robot in FIGS. 2A and 2B outfittedwith an armature and parked in front of a shelf shown in FIG. 1;

FIG. 4 is a partial map of the warehouse of FIG. 1 created using laserradar on the robot;

FIG. 5 is a flow chart depicting the process for locating fiducialmarkers dispersed throughout the warehouse and storing fiducial markerposes;

FIG. 6 is a table of the fiducial identification to pose mapping;

FIG. 7 is a table of the bin location to fiducial identificationmapping;

FIG. 8 is a flow chart depicting product SKU to pose mapping process;

FIG. 9 is a front view of an electrical charging assembly according tothis invention;

FIG. 10 is a side elevational view of the electrical charging assemblyof FIG. 9;

FIG. 11 is a perspective view of the electrical charging port of FIG.10;

FIG. 12 is a cross-sectional view of the electrical charging assemblymated with the electrical charging port;

FIG. 13A is a perspective view of the charger docking station accordingto this invention;

FIG. 13B is a perspective view of the charger docking station of FIG.14A with the exterior cover removed depicting the interior of thecharger docking station;

FIG. 14A is a front view of the charger docking station of FIG. 13A;

FIG. 14B is the front view of the charger docking station of FIG. 14Awith the exterior cover removed depicting the interior of the chargerdocking station;

FIG. 15A is a left side view of the charger docking station of FIG. 13A;

FIG. 15B is the left side view of the charger docking station of FIG.15A with the exterior cover removed depicting the interior of thecharger docking station;

FIG. 16A is a rear perspective view of the charger docking station ofFIG. 13A;

FIG. 16B is the rear perspective view of the charger docking station ofFIG. 16A with the exterior cover removed depicting the interior of thecharger docking station;

FIG. 17 is a top view of the charger docking station of FIG. 13A shownwith a docked robot;

FIG. 18 is a schematic view of a robot docking with the charging stationaccording to an aspect of this invention;

FIG. 19 is a schematic diagram of the electrical components of thecharging station;

FIG. 20 is a schematic diagram of certain electrical components of therobot utilized in the robot charging process;

FIG. 21 is a graph of discharge profile of a robot battery at varioustemperatures;

FIG. 22 is a flow chart depicting the robot charging process accordingto an aspect of the invention; and

FIG. 23 is a state diagram depicting the operation of the chargingstation according to an aspect of this invention.

DETAILED DESCRIPTION OF THE INVENTION

The disclosure and the various features and advantageous details thereofare explained more fully with reference to the non-limiting embodimentsand examples that are described and/or illustrated in the accompanyingdrawings and detailed in the following description. It should be notedthat the features illustrated in the drawings are not necessarily drawnto scale, and features of one embodiment may be employed with otherembodiments as the skilled artisan would recognize, even if notexplicitly stated herein. Descriptions of well-known components andprocessing techniques may be omitted so as to not unnecessarily obscurethe embodiments of the disclosure. The examples used herein are intendedmerely to facilitate an understanding of ways in which the disclosuremay be practiced and to further enable those of skill in the art topractice the embodiments of the disclosure. Accordingly, the examplesand embodiments herein should not be construed as limiting the scope ofthe disclosure. Moreover, it is noted that like reference numeralsrepresent similar parts throughout the several views of the drawings.

The invention is directed to an electrical charging system for use incharging robots. Although not restricted to any particular robotapplication, one suitable application that the invention may be used inis order fulfillment. The use of robots in this application will bedescribed to provide context for the electrical charging system.

While the description provided herein is focused on picking items frombin locations in the warehouse to fulfill an order for shipment to acustomer, the system is equally applicable to the storage or placing ofitems received into the warehouse in bin locations throughout thewarehouse for later retrieval and shipment to a customer. The inventionis also applicable to inventory control tasks associated with such awarehouse system, such as, consolidation, counting, verification,inspection and clean-up of products.

Referring to FIG. 1, a typical order-fulfillment warehouse 10 includesshelves 12 filled with the various items that could be included in anorder 16. In operation, the order 16 from warehouse management server 15arrives at an order-server 14. The order-server 14 communicates theorder 16 to a robot 18 selected from a plurality of robots that roam thewarehouse 10. Also shown is charging area 19, which is where one or morecharging stations according to an aspect of the invention may belocated.

In a preferred embodiment, a robot 18, shown in FIGS. 2A and 2B,includes an autonomous wheeled base 20 having a laser-radar 22. The base20 also features a transceiver (not shown) that enables the robot 18 toreceive instructions from the order-server 14, and a pair of digitaloptical cameras 24 a and 24 b. The robot base also includes anelectrical charging port 26 (depicted in more detail in FIGS. 10 and 11)for re-charging the batteries which power autonomous wheeled base 20.The base 20 further features a processor (not shown) that receives datafrom the laser-radar and cameras 24 a and 24 b to capture informationrepresentative of the robot's environment. There is a memory (not shown)that operates with the processor to carry out various tasks associatedwith navigation within the warehouse 10, as well as to navigate tofiducial marker 30 placed on shelves 12, as shown in FIG. 3. Fiducialmarker 30 (e.g. a two-dimensional bar code) corresponds to bin/locationof an item ordered. The navigation approach of this invention isdescribed in detail below with respect to FIGS. 4-8. Fiducial markersare also used to identify charging stations according to an aspect ofthis invention and the navigation to such charging station fiducialmarkers is the same as the navigation to the bin/location of itemsordered. Once the robots navigate to a charging station, a more precisenavigation approach is used to dock the robot with the charging stationand such a navigation approach is described below.

Referring again to FIG. 2B, base 20 includes an upper surface 32 where atote or bin could be stored to carry items. There is also shown acoupling 34 that engages any one of a plurality of interchangeablearmatures 40, one of which is shown in FIG. 3. The particular armature40 in FIG. 3 features a tote-holder 42 (in this case a shelf) forcarrying a tote 44 that receives items, and a tablet holder 46 (orlaptop/other user input device) for supporting a tablet 48. In someembodiments, the armature 40 supports one or more totes for carryingitems. In other embodiments, the base 20 supports one or more totes forcarrying received items. As used herein, the term “tote” includes,without limitation, cargo holders, bins, cages, shelves, rods from whichitems can be hung, caddies, crates, racks, stands, trestle, containers,boxes, canisters, vessels, and repositories.

Although a robot 18 excels at moving around the warehouse 10, withcurrent robot technology, it is not very good at quickly and efficientlypicking items from a shelf and placing them in the tote 44 due to thetechnical difficulties associated with robotic manipulation of objects.A more efficient way of picking items is to use a local operator 50,which is typically human, to carry out the task of physically removingan ordered item from a shelf 12 and placing it on robot 18, for example,in tote 44. The robot 18 communicates the order to the local operator 50via the tablet 48 (or laptop/other user input device), which the localoperator 50 can read, or by transmitting the order to a handheld deviceused by the local operator 50.

Upon receiving an order 16 from the order server 14, the robot 18proceeds to a first warehouse location, e.g. as shown in FIG. 3. It doesso based on navigation software stored in the memory and carried out bythe processor. The navigation software relies on data concerning theenvironment, as collected by the laser-radar 22, an internal table inmemory that identifies the fiducial identification (“ID”) of fiducialmarker 30 that corresponds to a location in the warehouse 10 where aparticular item can be found, and the cameras 24 a and 24 b to navigate.

Upon reaching the correct location, the robot 18 parks itself in frontof a shelf 12 on which the item is stored and waits for a local operator50 to retrieve the item from the shelf 12 and place it in tote 44. Ifrobot 18 has other items to retrieve it proceeds to those locations. Theitem(s) retrieved by robot 18 are then delivered to a packing station100, FIG. 1, where they are packed and shipped.

It will be understood by those skilled in the art that each robot may befulfilling one or more orders and each order may consist of one or moreitems. Typically, some form of route optimization software would beincluded to increase efficiency, but this is beyond the scope of thisinvention and is therefore not described herein.

In order to simplify the description of the invention, a single robot 18and operator 50 are described. However, as is evident from FIG. 1, atypical fulfillment operation includes many robots and operators workingamong each other in the warehouse to fill a continuous stream of orders.

The navigation approach of this invention, as well as the semanticmapping of a SKU of an item to be retrieved to a fiducial ID/poseassociated with a fiducial marker in the warehouse where the item islocated, is described in detail below with respect to FIGS. 4-8. Asnoted above, the same navigation approach may be used to enable therobot to navigate to a charging station in order to recharge itsbattery.

Using one or more robots 18, a map of the warehouse 10 must be createdand dynamically updated to determine the location of objects, bothstatic and dynamic, as well as the locations of various fiducial markersdispersed throughout the warehouse. To do this, one of the robots 18navigate the warehouse and build/update a map 10 a, FIG. 4, utilizingits laser-radar 22 and simultaneous localization and mapping (SLAM),which is a computational method of constructing or updating a virtualmap of an unknown environment. Popular SLAM approximate solution methodsinclude the particle filter and extended Kalman filter. The SLAMGMapping approach is the preferred approach, but any suitable SLAMapproach can be used.

Robot 18 utilizes its laser-radar 22 to create/update map 10 a ofwarehouse 10 as robot 18 travels throughout the space identifying openspace 112, walls 114, objects 116, and other static obstacles such asshelves 12 a in the space, based on the reflections it receives as thelaser-radar scans the environment.

While constructing the map 10 a or thereafter, one or more robots 18navigates through warehouse 10 using cameras 24 a and 24 b to scan theenvironment to locate fiducial markers (two-dimensional bar codes)dispersed throughout the warehouse on shelves proximate bins, such as 32and 34, FIG. 3, in which items are stored. Robots 18 use a knownreference point or origin for reference, such as origin 110. When afiducial marker, such as fiducial marker 30, FIGS. 3 and 4, is locatedby robot 18 using its cameras 24 a and 24 b, the location in thewarehouse relative to origin 110 is determined. By using two cameras,one on either side of robot base, as shown in FIG. 2A, the robot 18 canhave a relatively wide field of view (e.g. 120 degrees) extending outfrom both sides of the robot. This enables the robot to see, forexample, fiducial markers on both sides of it as it travels up and downaisles of shelving.

By the use of wheel encoders and heading sensors, vector 120, and therobot's position in the warehouse 10 can be determined. Using thecaptured image of a fiducial marker/two-dimensional barcode and itsknown size, robot 18 can determine the orientation with respect to anddistance from the robot of the fiducial marker/two-dimensional barcode,vector 130. With vectors 120 and 130 known, vector 140, between origin110 and fiducial marker 30, can be determined. From vector 140 and thedetermined orientation of the fiducial marker/two-dimensional barcoderelative to robot 18, the pose (position and orientation) defined by aquaternion (x, y, z, ω) for fiducial marker 30 can be determined.

Flow chart 200, FIG. 5, describing the fiducial marker location processis described. This is performed in an initial mapping mode and as robot18 encounters new fiducial markers in the warehouse while performingpicking, placing and/or other tasks. In step 202, robot 18 using cameras24 a and 24 b captures an image and in step 204 searches for fiducialmarkers within the captured images. In step 206, if a fiducial marker isfound in the image (step 204) it is determined if the fiducial marker isalready stored in fiducial table 300, FIG. 6, which is located in memory34 of robot 18. If the fiducial information is stored in memory already,the flow chart returns to step 202 to capture another image. If it isnot in memory, the pose is determined according to the process describedabove and in step 208, it is added to fiducial to pose lookup table 300.

In look-up table 300, which may be stored in the memory of each robot,there are included for each fiducial marker a fiducial identification,1, 2, 3, etc., and a pose for the fiducial marker/bar code associatedwith each fiducial identification. The pose consists of the x,y,zcoordinates in the warehouse along with the orientation or thequaternion (x,y,z, ω).

In another look-up Table 400, FIG. 7, which may also be stored in thememory of each robot, is a listing of bin locations (e.g. 402 a-f)within warehouse 10, which are correlated to particular fiducial ID's404, e.g. number “11”. The bin locations, in this example, consist ofseven alpha-numeric characters. The first six characters (e.g. L01001)pertain to the shelf location within the warehouse and the lastcharacter (e.g. A-F) identifies the particular bin at the shelflocation. In this example, there are six different bin locationsassociated with fiducial ID “11”. There may be one or more binsassociated with each fiducial ID/marker. Charging stations located incharging area 19, FIG. 1, may also be stored in table 400 and correlatedto fiducial IDs. From the fiducial IDs, the pose of the charging stationmay be found in table 300, FIG. 6.

The alpha-numeric bin locations are understandable to humans, e.g.operator 50, FIG. 3, as corresponding to a physical location in thewarehouse 10 where items are stored. However, they do not have meaningto robot 18. By mapping the locations to fiducial ID's, robot 18 candetermine the pose of the fiducial ID using the information in table300, FIG. 6, and then navigate to the pose as described herein.

The order fulfillment process according to this invention is depicted inflow chart 500, FIG. 8. In step 502, warehouse management system 15,FIG. 1, obtains an order, which may consist of one or more items to beretrieved. In step 504 the SKU number(s) of the items is/are determinedby the warehouse management system 15, and from the SKU number(s), thebin location(s) is/are determined in step 506. A list of bin locationsfor the order is then transmitted to robot 18. In step 508, robot 18correlates the bin locations to fiducial ID's and from the fiducial s,the pose of each fiducial ID is obtained in step 510. In step 512 therobot 18 navigates to the pose as shown in FIG. 3, where an operator canpick the item to be retrieved from the appropriate bin and place it onthe robot.

Item specific information, such as SKU number and bin location, obtainedby the warehouse management system 15, can be transmitted to tablet 48on robot 18 so that the operator 50 can be informed of the particularitems to be retrieved when the robot arrives at each fiducial markerlocation.

With the SLAM map and the pose of the fiducial ID's known, robot 18 canreadily navigate to any one of the fiducial ID's using various robotnavigation techniques. The preferred approach involves setting aninitial route to the fiducial marker pose given the knowledge of theopen space 112 in the warehouse 10 and the walls 114, shelves (such asshelf 12) and other obstacles 116. As the robot begins to traverse thewarehouse using its laser radar 22, it determines if there are anyobstacles in its path, either fixed or dynamic, such as other robots 18and/or operators 50, and iteratively updates its path to the pose of thefiducial marker. The robot re-plans its route about once every 50milliseconds, constantly searching for the most efficient and effectivepath while avoiding obstacles.

Generally, localization of the robot within warehouse 10 a is achievedby many-to-many multiresolution scan matching (M3RSM) operating on theSLAM virtual map. Compared to brute force methods, M3RSM dramaticallyreduces the computational time for a robot to perform SLAM loop closureand scan matching, two critical steps in determining robot pose andposition. Robot localization is further improved by minimizing the M3SRM search space according to methods disclosed in related U.S.application Ser. No. 15/712,222, entitled MULTI-RESOLUTION SCAN MATCHINGWITH EXCLUSION ZONES, filed on Sep. 22, 2017, and incorporated byreference in its entirety herein.

With the product SKU/fiducial ID to fiducial pose mapping techniquecombined with the SLAM navigation technique both described herein,robots 18 are able to very efficiently and effectively navigate thewarehouse space without having to use more complex navigation approachestypically used which involve grid lines and intermediate fiducialmarkers to determine location within the warehouse.

Generally, navigation in the presence of other robots and movingobstacles in the warehouse is achieved by collision avoidance methodsincluding the dynamic window approach (DWA) and optimal reciprocalcollision avoidance (ORCA). DWA computes among feasible robot motiontrajectories an incremental movement that avoids collisions withobstacles and favors the desired path to the target fiducial marker.ORCA optimally avoids collisions with other moving robots withoutrequiring communication with the other robot(s). Navigation proceeds asa series of incremental movements along trajectories computed at theapproximately 50 ms update intervals. Collision avoidance may be furtherimproved by techniques described in related U.S. application Ser. No.15/12,256 entitled DYNAMIC WINDOW APPROACH USING OPTIMAL RECIPROCALCOLLISION AVOIDANCE COST-CRITIC, filed on Sep. 22, 2017 and incorporatedby reference in its entirety herein.

As described above, robots 50 need to be periodically re-charged. Inaddition to marking locations in the warehouse where items are stored, afiducial marker may be placed at one or more electrical chargingstation(s) within the warehouse. When robot 18 is low on power it cannavigate to a fiducial marker located at an electrical charging stationso it can be recharged. Once there it can be manually recharged byhaving an operator connect the robot to the electrical charging systemor the robot can use its navigation to dock itself at the electricalcharging station.

As shown in FIGS. 9 and 10, electrical charging assembly 200 may be usedat an electrical charging station. Electrical charging assembly 200includes charger base 202 on which are disposed a first male terminalmember 204 and a second male terminal member 206. Although not shown inthis figure, a positive electrical input from the electrical service inthe warehouse would be affixed to charger base 202 and electricallyconnected to one of the first male terminal member 204 or the secondmale terminal member 206. Also, a negative electrical input would beaffixed to charger base 202 and electrically connected to the other ofthe first male terminal member 204 or the second male terminal member206.

First male terminal member 204 has first base 210 affixed to andextending orthogonally along a first axis 212 from surface 214 of thecharger base 202 and terminates in a first electrical contact 216. Firstelectrical contact 216 may be in the form of a copper bus bar whichextends into charger base 202 to which would be affixed one of thepositive or negative electrical connections. Second male terminal member206 has second base 220 affixed to and extending orthogonally along asecond axis 222 from surface 214 of the charger base 202 and terminatesin a second electrical contact 226. Second electrical contact 226 mayalso be in the form of a copper bus bar which extends into charger base202 to which would be affixed the other of the positive or negativeelectrical connections.

The first male terminal member 204 has a plurality of external surfacesat least two of which have a curved shape from the first base 210 to thefirst electrical contact 216 forming a concave surface. In theembodiment depicted in FIGS. 9 and 10 there are three curved surfaces;namely, top curved surface 230 and opposing side curved surfaces 232 and234, the three of which curve from first base 210 to first electricalcontact 216, with particular radii of curvature, forming concavesurfaces. In this embodiment, the radius of curvature of opposing sidecurved surfaces 232 and 234 is approximately 63.9 mm. The radius ofcurvature of top curved surface 230 is approximately 218.7 mm. Thesewere determined empirically to provide for optimized alignmentcorrection. More misalignment is expected in the horizontal direction ascompared to the vertical direction; therefore, the opposing side curvedsurfaces are provided with a smaller radius of curvature. Of course, theradii of curvature of the curved surfaces may be varied depending on theapplication.

In addition, first male terminal member 204 has a flat surface 236 whichis substantially parallel to first axis 212 and orthogonal to surface214 of charger base 202. Flat surface 236 includes a recessed surfaceportion 238 proximate first electrical contact 216.

The second male terminal member 206 has a plurality of external surfacesat least two of which have a curved shape from the second base 220 tothe second electrical contact 226, forming a concave surface. In theembodiment depicted in FIGS. 9 and 10 there are three curved surfaces;namely, bottom curved surface 240 and opposing side curved surfaces 242and 244, the three of which curve from first base 220 to firstelectrical contact 226, with particular radii of curvature, formingconcave surfaces. In this embodiment, the radius of curvature ofopposing side curved surfaces 242 and 244 is approximately 63.9 mm. Theradius of curvature of bottom curved surface 240 is approximately 218.7mm. These were determined empirically to provide for optimized alignmentcorrection. More misalignment is expected in the horizontal direction ascompared to the vertical direction; therefore, the opposing side curvedsurfaces are provided with a smaller radius of curvature. Of course, theradii of curvature of the curved surfaces may be varied depending on theapplication.

In addition, second male terminal member 206 has a flat surface 246,which is substantially parallel to second axis 222 and orthogonal tosurface 214 of charger base 202. Flat surface 246 includes a flaredsurface portion 248 proximate second electrical contact 226.

There is a cavity 250 formed between the first male terminal member 204and the second male terminal member 206 defined by the at least one flatsurface 236 of the first male terminal member 204 and the at least oneflat surface 246 of the second male terminal member 206. Cavity 250 hasan opening 252 between the first electrical contact 216 and the secondelectrical contact 226. At opening 252, the recessed surface portion 238of flat surface 236 and the flared surface portion 248 of flat surface246, are present.

Referring again to FIGS. 9 and 10, metal contacts 260 a-e are disposedon charger base 202. These metal contacts engage with correspondingmagnets on electrical charging port 300, described below, and secureelectrical charging assembly 200 and electrical charging port 300 inplace while charging. Alternatively, the magnets could be disposed onthe charger base 202 with the metal contacts on charging port 300.

If the robot is docking to a fixed electrical charging station, it mayuse camera 24 a and 24 b to maneuver it into position so that electricalcharging port 300 can mate with electrical charging assembly 200. Thecameras may use the fiducial markers associated with the chargingstation as a reference point for fine localization, which will bedescribed in more detail below. As the robot maneuvers into place,achieving perfect alignment for mating of the electrical contacts 216and 226 of the electrical assembly 200 with electrical contacts 304 and306, respectively, of electrical charging port 300 can be difficult.Therefore, electrical charging assembly 200 and electrical charging port300 have been specifically designed in order to ensure easier, moreefficient, and less problematic mating to allow the robots toelectrically re-charge more quickly.

As can be seen in FIGS. 11 and 12, electrical charging port 300 includesa first cavity 308 and second cavity 310, which are configured toreceive and engage with first male terminal member 204 second maleterminal member 206, respectively, of electrical charging assembly 200,as robot base 20 a is docking. Cavity 308 has concave, curved surfaces312 which are complimentary to the curved surfaces 230, 232 and 234 offirst male terminal member 204. In other words, the first cavity 308 mayinclude curved surfaces 312 having radii of curvature substantiallyequal to the radii of curvature of the curved external surfaces (230,232, and 234) of first male terminal member 204. Substantially equal inthis case means just slightly larger to allow insertion and removal offirst male terminal member 204 in cavity 308. Cavity 310 also hasconcave, curved surfaces 314 which are complimentary to the curvedsurfaces 240, 242 and 244 of second male terminal member 206. In otherwords, the second cavity 310 may include curved surfaces 314 havingradii of curvature substantially equal to the radii of curvature of thecurved external surfaces (240, 242, and 244) of second male terminalmember 206. Substantially equal in this case means just slightly largerto allow insertion and removal of second male terminal member 206 incavity 310.

The openings of cavities 308 and 310 are wider and longer than thewidth/length of the electrical contacts 216/226 of first male terminalmember 204 second male terminal member 206. The extra width/lengthallows the first male terminal member 204 second male terminal member206 to be more easily received within cavities 308 and 310 even if theyare somewhat misaligned in the horizontal/vertical directions during themating process. As the robot moves toward electrical charging assembly200, the engagement of the complimentarily curved surfaces cause thefirst male terminal member 204 and the second male terminal member 206to be guided into alignment so that engagement between electricalcontacts 216/226 of electrical charging assembly and electrical contacts304/306 of electrical charging port 300 will occur.

Thus, the radii of mating parts (male terminal members and cavities) aredesigned to provide coarse alignment when the male terminal members arefirst inserted into the cavities, and fine adjustment as full insertionis approached.

The electrical charging system provides an additional feature for easiervertical alignment. This is accomplished by the interaction of divider320, which is between cavities 308 and 310, in combination with opening352 of cavity 350 of electrical charging assembly 200. Flared surfaceportion 248 provides a wider opening so, if there is verticalmisalignment, it causes the divider 320 to ride up vertically into placein cavity 350, as the docking process occurs.

When the first and second male terminals 204 and 206 are fully insertedinto cavities 308 and 310, electrical charging assembly 200 is securedin place with electrical charging port 300 by means of magnets 360 a-e,which engage with metal contacts 260 a-e on electrical charging assembly200. The magnets may be disposed beneath the external surface ofelectrical charging port 300 and, as such, they are shown in phantom.

There is an additional feature included in the electrical chargingsystem, which is useful in the case of manual charging by an operator.If the electrical charging assembly 200 were inserted into theelectrical charging port 300 improperly, i.e. upside down withelectrical contact 216 of electrical charging assembly 200 connected toelectrical contacts 306 of electrical charging port 300 and withelectrical contact 226 of electrical charging assembly connected toelectrical contacts 304 of electrical charging port 300, the polaritieswould be reversed and significant damage to robot base 20 a wouldresult.

To prevent this from happening, a stop 330 (see FIGS. 11 and 12) isincluded on the surface of divider 320 of electrical charging port 300.The stop 330 has an angled surface portion 332 and flat surface portion334. As shown in FIG. 10, within cavity 250 of electrical chargingassembly 200, there is a recessed surface portion 238, which allows forfull insertion of electrical charging assembly 200 into electricalcharging port 300. Recess 238 allows for clearance by first maleterminal member 204 of stop 330 as the angled surface portion 332 andthe flat surface portion 334 of stop 330 engage with the angled portionand flat portion of recessed surface portion 238 like a puzzle piece. Ifthe electrical charging assembly 200 were upside down, when insertedinto electrical charging port 300 surface 246 of second male terminalmember 206 would contact stop 330 and be prevented from full insertionand contact with electrical contacts 304.

As shown in FIG. 12, when electrical contacts 216 and 226 of maleterminal members 204 and 206, respectively, engage with electricalcontacts 304 and 306, the electrical contacts 304 and 306 arecompressed, as these contacts may be in the form of spring loaded pins.Electrical contacts 304 and 306 may be compressed from their fullyextended position at line 400 to their compressed position (not shown)at line 402. Each of electrical contacts 304 and 306 are shown toinclude five spring loaded pins. The number of pins used is dependentupon the expected electrical current to be carried during the chargingprocess and the capacity of the individual pins. The use of multiplespring loaded pins for the electrical contacts is beneficial to ensureproper contact with the electrical contacts 216 and 226 of male terminalmembers 204 and 206 even in the case of manufacturing variations andwear on components.

When electrical contacts 304 and 306 are in the compressed position,magnets 360 a-e of electrical charging port 300 are in close proximitywith metal contacts 260 a-e of electrical charging assembly 200 and theymagnetically engage to secure in place electrical charging assembly 200and electrical charging port 300. In this position, it can be seen thatupper and lower curved surfaces 230 and 240 of male terminal members 204and 206, respectively, are complimentarily engaged with surfaces 312 and314 of cavities 308 and 310, respectively.

Also depicted in FIG. 12 are bus bar 410 of first male terminal member204 and bus bar 412 of second male terminal member 206. The bus bars areconnected to mount 414 to affix them within electrical charging assembly200 at the end opposite electrical contacts 216 and 226.

A charger docking station 500 according to an aspect of this inventionis depicted in FIGS. 13-16 and 17. Referring particularly to FIGS. 13and 14, charger docking station 500 includes electrical chargingassembly 200, as described above, which projects from front cover 502 ofcharger docking station 500. Electrical charging assembly 200 is mountedto charger docking station 500 on U-shaped rubber bellows mount 504 inorder to seal opening 506 in front cover 502 while also allowingelectrical charging assembly 200 to move in six degrees of freedom (aswill be described below) to facilitate a smooth docking process of arobot when recharging is needed.

Also shown is protective bumper 508, which may be made of metal, mountedhorizontally across the bottom portion of front cover 502 to protect thecharger docking station 500 from damage in the event that a robot doesnot smoothly dock. Charger docking station 500 further includes rightside cover 510 and left side cover 512 (not visible in FIG. 13A). Inright side cover opening 514 a is located grip area 516 a which allows ahand to be inserted for more easily lifting the charger docking station500, as shown in FIG. 15A. Although not visible in this view, a similaropening and grip area is included in left side cover 512, which aredepicted in FIG. 16A as opening 514 b and grip area 516 b. Also shown inan opening at the back of right side cover 510 are vents 518 a toprovide cooling for the electrical components within charger dockingstation 500. A similar vent 518 b is included in the left side cover 512visible in FIG. 16A.

A metal frame comprising front frame member 520 a, right side framemember 520 b, left side frame member 520 c, and back side frame member520 d are interconnected to form the base structure for charger dockingstation 500. Referring to FIG. 13B, each of the frame members is securedto a floor in the warehouse by means of bolts 521 a-d and protectivebumper 508 is secured to metal frame 520 via front frame member 520 a.Since protective bumper 508 is external to and protrudes out from frontcover 502, it is the first point of impact with a robot as it docks withcharger docking station 500. In the event of an inadvertent high forceimpact by a robot, such high forces will be imparted on the protectivebumper rather than the front cover 502. Front cover 502 as well as rightside cover 510 and left side cover 512 are typically made a hard plasticmaterial and are susceptible to cracking/breaking if impacted by arobot. The forces imparted on the protective bumper 508 are furtherdiverted to metal frame 520 through front frame member 520 a. Frontframe member 520 a comprises a C-shaped member that extends across thewidth of charging station 500 and a flange integral with and extendingfrom a top surface of the C-shaped member. Protective bumper 508interconnects to the flange via a plurality of apertures in front cover502. The forces from bumper 508 are transmitted to the front framemember through the flange and c-shaped member and further transmitted tothe right, left and back side frame members 520 b-d. Ultimately theforces are transmitted through bolts 521 a-d to the warehouse floor.Thus, this protective bumper system absorbs and diverts forces impartedby a robot away from the hard plastic front cover 502, protecting itfrom damage.

Top cover 524, which is also made of a hard plastic material, includes auser interface panel 526 disposed in a cavity in the surface of topcover 524 which may include certain indicators and controls for a userto operate the charger docking station. For example, lighting signals toindicate various states such as “Ready”, “Charging”, “Power On”,“Recovery Mode”, and “Fault” or “E-Stop” may be included. Buttons suchas “Power on/off”, “Start manual charge”, “Undock”, “Reset”, and“E-Stop” may be included.

Along the back edge of top cover 524 is a back panel 528, whichcomprises a center panel section 530 and side panel sections 532 and 534on the right and left sides, respectively, of center panel 530. Centerpanel 530 has a rectangular front surface 536 which is substantiallyparallel to front cover 502. Right side panel 532 has a rectangularfront surface 538 and left side panel 534 has a rectangular frontsurface 540.

Right and left side panels 532 and 534 have wide sidewalls 542 and 544,respectively, on one side and converge to narrower widths on the othersides which interconnect with center panel section 530. Thus, right andleft side panels 532 and 534 and wedge-shaped. As a result, their frontsurfaces 538 and 540 are not parallel with front surface 536 of centerpanel 530 or front cover 502. They are each disposed at an angle, θ,with respect to surface 536. Fiducial markers 546 and 548 (e.g. atwo-dimensional bar code) disposed on front surfaces 538 and 540,respectively, are also disposed at the angle, θ, relative to frontsurface 536 and the front cover 502.

As will be described in detail below, the robots use the angled fiducialmarkers for precision navigation during the process of docking with thecharger docking station by viewing them with their onboard cameras. Togenerally navigate to the charger docking station when recharging isneeded, the robots navigate in the same manner as they do whennavigating to product bins as described above. Charging station 500 maybe associated with a pose located in close proximity to the front cover502 and generally aligned (rotationally) such that the robots' onboardcameras are facing toward back panel 528.

Referring to FIGS. 13B and 14B, compliant members 550 a-d, which mayinclude springs, are connected to legs 551 a-d (legs 551 c and 551 d arenot visible), respectively, on electrical charging assembly 200 to allowa certain amount of movement in all six degrees of freedom to accountfor small errors in navigating the robot to the charger docking stationwhile still enabling proper mechanical and electrical connection betweenthe electrical charging assembly 200 and electrical charging port 300,as shown in FIG. 12, for example.

In addition, as can be seen in FIG. 15B, gas spring 552 is connected toelectrical charging assembly 200 to stabilize it as it moves along theaxis of gas spring 552 as indicated by arrows 554 and 555. Gas spring552 is mounted on frame 556 which is affixed to floor panel 558 of thecharger docking station 500. As the robot moves toward charger dockingstation 500 during the mating process, electrical charging port 300(described above) contacts electrical charging assembly 200 and appliesa force in the direction of arrow 554. Gas spring 552 providesresistance in the direction of arrow 555 sufficient to allow some amountof movement during mating of electrical charging port 300 withelectrical charging assembly 200 but prevent excessive movement in thedirection of arrow 554 to act as a stop and ensure proper mating.

In addition, as the electrical charging port 300 is being retracted fromthe electrical charging assembly 200 during the un-mating process, dueto the magnetic connection between the electrical charging assembly 200and the electrical charging port 300 (described above), electricalcharging assembly 200 will be pulled in the direction of arrow 555 untilthe magnetic force is overcome. Gas spring 552 also ensures that themovement is limited, by providing a force in the direction of arrow 554.

While the electrical charging port 300 (which is the female portion ofthe connector) is described herein to be mounted on the robot and theelectrical charging assembly 200 (which is the male portion of theconnector) is described herein as being mounted on the charging station,of course, these components could be reversed. In which case theelectrical charging port 300 would be mounted on the charging stationand the electrical charging assembly 200 would be mounted on the robot.Moreover, as will be apparent to those skilled in the art, other chargerports and designs may be used in connection with the embodimentsdescribed herein.

Referring again to FIG. 13B, top panel 560, which is supported in partby frame legs 562 and 564 mounted on floor panel 558, includes a cavityin which are housed controller board 572 and an infrared (IR)transceiver board 574. Controller board 572 provides overall control ofcharger docking station 500, including activating the chargingprotocols, selecting charging parameters and profiles, monitoringcharging conditions and status (e.g. charging state and batterytemperature) and communications with the robot, all of which aredescribed in more detail below. The IR transceiver board 574 is used forcommunication with the robot during the docking and charging processesand may utilize an IrDA (Infrared Data Association) communicationsprotocol.

Continuing to refer to FIG. 13B as well as FIG. 15B, back wall panel 580is shown to support power supply 582 which is powered by the warehousepower. Back wall panel 580 may also function as a heat sink for powersupply 582 and may be made of a different metal than the other panels tobetter conduct heat. Back panel 580 further supports top panel 560 alongwith frame legs 562 and 564. The warehouse power is fed to chargerdocking station 500 through connector 584, which may be an IECconnector, for example. Wall 586 connected to floor panel 558 andpositioned adjacent to connector 584 may be used to provide additionalprotection for the power supply to the charger docking station

FIGS. 16A and 16B provide a perspective view from the rear of chargerdocking station 500 with the cover on and off, respectively. These viewsalso allow for the right side of charger docking station to be seen. InFIG. 16A back wall 580 is shown to include a port 592 through which thepower supply from the house is fed to connect to electrical connector584. The back of electrical connector 584, can be seen protrudingthrough a hole in back wall 580, FIG. 16B.

Robot Docking

The docking of a robot to the electrical charging station 500 forrecharging is described with regard to FIGS. 17 and 18. In FIG. 17,robot 18 having electrical charging port 300 is shown mated toelectrical charging assembly 200 of charging station 500. Robot 18 may,for example, navigate to location 600, which is defined by a pose storedfor the charging station. Navigation to pose 600 is undertaken in themanner described above for navigating robots throughout the warehouse tovarious bin locations. Once at pose 600, a precision navigation processis undertaken to position the robot 18 at location 602, in whichlocation the electrical charging port 300 is mated with electricalcharging assembly 200 and robot 18 is docked at charging station 500 forrecharging.

The orientation of surfaces 538 and 540 (and fiducials 546 and 548,respectively) relative to cameras 24 a and 24 is described with regardto FIG. 18. As shown in FIG. 18, robot 18 is located at position 602,thus it is docked at charging station 500. In this position, the fieldof view Φ (approximately 79.4 degrees) of camera 24 a is shown to spanacross surfaces 536 and 538. The optical axis 610 (i.e. the centerlineof the field of view or Φ/2) of camera 24 a intersects surface 38 andfiducial 46 at a substantially perpendicular angle. In addition, in thisposition, the field of view Φ (approximately 79.4 degrees) of camera 24b is shown to span across surfaces 536 and 540, slightly overlapping thefield of view of camera 24 a. The combined field of views of the camerasprovides the robot 18 with an effective field of view of approximately120 degrees. The combined field of few is less than the sum of thefields of view of the cameras, due to the overlapping sections creatinga blind spot for the robot.

The optical axis 612 (i.e. the centerline of the field of view or Φ/2)of camera 24 b intersects surface 40 and fiducial 48 at a perpendicularangle. In order to ensure that when docked the optical axes of thecameras will be aligned perpendicular to surfaces, 538 and 540, theangle θ 0 which is the orientation of surfaces 538 and 540 relative tosurface 536 must be properly set. In this example, the angle θ isapproximately 150 degrees. By positioning the fiducials in this manner,the visibility of the fiducials by the cameras 24 a and 24 b isincreased.

As described above, since the cameras are offset from the center of therobot they combine to provide a wide field of view. However, theorientation of the cameras make viewing the fiducials on the chargingstation challenging. To address this issue, the fiducials may beoriented at an angle to better align with the cameras, which makes thefiducials easier to more accurately read. This may be accomplished byorienting the optical axis of the camera to be at a substantiallyperpendicular angle to and centered on the fiducial when the robot is inthe docked position, as is shown in FIG. 18.

Controlling robot 18 so that it mates with the charging station 500, mayrequires a more precise navigation approach than that used to navigatethe robot to pose 600. Once at pose 600, the robot may make use of theperceived positions and orientations of the fiducials 546 and 548 onsurfaces 538 and 540, respectively, in its camera frames. At pose 600,robot 18 is close enough to perceive fiducials 546 and 548 and isapproximately centered on charging station 500. A docking controlalgorithm may be used which permits for errors in the robot navigatingto this initial pose location. In other words, the navigation approachused to arrive at pose 600, which may use 5 cm-resolution maps, may notbe precisely position at the pose location. While positioned nominallyat pose 600, robot 18 obtains information about the position andorientation of fiducials 546 and 548 using its cameras 24 a and 24 b. Asit moves toward charging station 500, it attempts to minimize two errorquantities as follows:

(1) Each camera will detect one fiducial: the left and right cameraswill detect the left and right fiducials, respectively. The fiducials,once detected, can be transformed internally so that to the robot, theyappear to be perfectly perpendicular to the path of the robot (i.e.,“flat”, as perceived from the camera, rather than appearing skewed). Wecan then detect the relative sizes of each fiducial marker, and use thatto determine if the robot is closer to one fiducial than the other. Thisindicates that the robot is not perfectly centered in its approach, andneeds to move towards the center line. If we refer to the pixel area ofthe corrected left fiducial as S_(L) and the pixel area of the correctedright fiducial as S_(R), then the robot needs to minimize |S_(R)−S_(L)|.

(2) Within the left camera image, the left dock fiducial will be somenumber of pixels from the right side of the image. We will call thisnumber D_(L). Likewise, the for the right camera image, the right dockfiducial will be some number of pixels D_(R) from the left side of theimage. The robot therefore needs to minimize |D_(R)−D_(L|.)

As the robot needs to correct for the error in (1) first, we issue aconstant linear velocity to the robot, and issue a rotational velocityof k_(S) (S_(R)−S_(L)) to the robot until this value gets below somethreshold T_(S). The term k_(S) is a proportional control constant whosevalue is in the range (0, 1]. When the threshold T_(S) is satisfied, therobot attempts to minimize the error in (2) by issuing a rotationalvelocity to the robot of k_(D) (D_(R)−D_(L)), where k_(D) is also aproportional control constant in the range of (0, 1]. We continue doingthis until either (a) the robot reaches the dock, or (b) the error|S_(L)−S_(R)| grows outside the threshold T_(S), at which point weswitch back to minimizing the error in (1).

The above described precision navigation approach is one example ofvarious approaches that could be used to dock robot 18 with chargingstation 500.

Robot Charging Hardware

The robots described in the preferred embodiment are configured toautomatically mate with a charging station during normal “live”operation, i.e. the robots remain under power during charging and theymay exchange information with the charging station while mated viaoptical communications or otherwise. For example, the charging stationobtains the temperature of the robot's batteries during charging, whilethe robot obtains the amount of charge transferred to the batteries fromthe charging station.

Referring to FIG. 19, controller board 572 provides overall control ofcharging station 500, including activating the charging protocols,selecting charging parameters and profiles (based on battery/robottype), monitoring charging conditions and status (e.g. charging stateand battery temperature) and communications with the robot. The IRtransceiver board 574 may be used for communication with the robotduring the docking and charging processes and may utilize an IrDA(Infrared Data Association) communications protocol. Communicationsbetween robot and the charging station may be implemented in variousknown ways, including via wired connection. The charging station alsoincludes male electrical charging assembly 200 which, when the robot isdocked, mates with the female electrical charging port 300 of the robot.It will be understood by those skilled in the art that other forms ofelectrical connectors may be used, including gender-less flat platesdisposed on insulating surfaces.

There is a power supply 582, which may be a voltage programmable powersupply, and a current sensor board 650 for sensing the amount of chargeoutput from power supply 582 to the robot via male electrical chargingassembly 200 when mated with female electrical charging port 300 on therobot. The IR transceiver board 574, power supply 582, and currentsensor board 650 are each interconnected to microprocessor 700 oncontroller board 572. Microprocessor 700 may be an ST MicrosystemsCortex M4 derivative or other Cortex or comparable type of processor.

In one embodiment, the charging station 500, may be capable ofaccommodating the charging requirements of LiFePO4 (Lithium IronPhosphate) batteries using a three-phase charging profile, which may bea typical battery used in the robots of the type described herein. Forthis battery type, a 1 kW power supply providing a 1.5 C charge ratewould meet these constraints. However, it will be understood that thecharging station 500 may be capable of charging various battery typeswith different charging requirements.

Continuing to refer to FIG. 19, controller board 572 may include lowdrop-out (LDO) regulators 702 to provide well-regulated +3.3V and 1.8V(or as-needed) internal supply voltages which are powered by theauxiliary 5V output of power supply 582. The controller board may alsoinclude a power supervisory circuit 704 capable of resetting themicroprocessor 700 on power-on, power interruption, watchdog timeout, ormanual button press cases. With respect to microprocessor 700 I/Ofunctions, there is an output 706 from microprocessor 700 to turn onmain output of power supply 582 to enable charging and an input 708 frompower supply 582 to sense that main output 710 power supply 582 isfunctioning.

Microprocessor 700 controls the output of power supply 582 via voltageinput provided by buffered analog output 712. A scaled and bufferedanalog voltage input 714 taken from the output 710 of the power supply582 along with precision reference voltage from voltage referencecircuit 716 are input to microprocessor 700 to monitor charging voltagebeing provided to the robot during charging. In addition, bufferedanalog current input 718 taken from current sensor board 650 is used bymicroprocessor 700 to monitor charging current being output to therobot.

Controller board 572 has several ports and inputs/outputs, includingcommunications interface 720 which allows for RS485 serialcommunications between microprocessor 700 and IrDA board 574. This, inturn, allows for infrared communications between charging station 500and the robot. There is an Ethernet port 722 to permit debug/diagnosticsvia a terminal shell and a micro USB connector and pushbutton 724 toprovide access to device firmware update (DFU) bootloader. Also, thereare outputs 726 to drive four high-brightness LEDs forready/charging/fault indication on a display on user interface panel526.

In one embodiment, power supply 582 may be a Meanwell RSP-1000-27 powersupply, which is capable of providing a 37 A output current. Input power730 to power supply 582 may be 120VAC from the internal power from thewarehouse. The main power supply output voltage/current 710 may becontrolled by the microprocessor 700 by actively driving an input pin bybuffered analog output 712 using a voltage ranging from 2.5V to 4.5volts to control charging supply current (constant current phase) orvoltage (constant voltage phase). The supply output voltage/current 710may be adjusted, for example, to output 30V open circuit with a 4.5Vinput delivered by buffered analog output 712. The S− and S+ sense pins732 may sense the current/voltage output 710 and be used as feedback forpower supply 582.

As the current is being provided to the robot from the charging station500 via charging assembly 200, the charging current may be measuredusing a hall sensor on current sensor board 650 connected to thepositive output of the power supply 582. The measurement range of sensorboard 650 may be positive-only over a range of 0-50 A and a bufferedanalog current input 718 taken from current sensor board 650 may be usedby microprocessor 700 to monitor charging current (and total charge)being output to the robot. And, as the current is being provided to therobot, the voltage present at the charging assembly 200 may be sensed byproviding a voltage signal from the positive side output of power supply582 which may be scaled, buffered and fed by 714 to microprocessor 700.Nominal voltage range may typically be up to 32V full scale. Thenegative side of the charging assembly 200 may be connected to theground plane of the controller 700.

Referring to FIG. 20, the hardware components on the robot, such asrobot 18 of FIGS. 17/18, pertaining to the charging system of thisdisclosure are shown. Battery pack 800, which may include, for example,two LiFePO4 (Lithium Iron Phosphate) batteries each having a 13.5Vopen-circuit voltage and 32 Ah capacity, is connected to electricalcharging port 300 via fuse 801 on the positive terminal. The batterypack 800 is also connected to motor controller 802 via fuse 803 on thepositive line from the battery and to DC to DC converters (not shown)via lines 804 to power various other components, such as robotcontroller, optical cameras, and Lidar.

It should be noted that the system herein does not require a batterypack with a full battery management system including circuitry tomonitor battery charge state. The state of charge of the battery withthe system herein is monitored using a distributed monitoring approachshared between the robot and the charging station which is described indetail below. As a result, a less expensive battery management systemmonitoring only safety related parameters such as voltage, temperature,and current is needed.

Motor controller 802 may include a current sensor 806, such as a hallsensor, in line with the positive connection of battery 800 and themotor drive circuit 808, which drives electric motors 810 and 812 topropel the robot. A voltage sensor 807 to measure the output voltage ofbattery 800 is may also be provided. There is a processor 814 on themotor controller 802, which among other things, controls the motor drivecircuit 808 based on control signals received from the overall robotcontroller (not shown) and tracks the amount of current used by thebattery to power electric motors 810 and 812 via the motor controller802, as detected by current sensor 806. Processor 814 also uses thesensed current to determine the total charge usage by the measuredcurrent over time.

The amount of charge provided to the robot during charging by chargingstation 500 is determined by current sensor board 650, as describedabove. Also, as described above, IrDA board 574 on the charging station500 allows for infrared communications between the charging station 500and robot 18, which itself includes an IrDA board 816 connected to an RS485 interface within motor controller 802. Periodically (e.g. once persecond), the amount of charge transferred from the charging station tothe robot may be communicated to robot 18 via infrared communicationsand saved in memory, which may be on the motor controller 802. Whencharging is completed, as described below, the starting or initialcoulomb count will be known by the robot.

When the robot leaves the charging dock, the amount of charge used topower the electric motors and controller board, as described above, maybe periodically determined (e.g. once per second) and then subtractedfrom the amount of charge provided during charging (initial coulombcount) to determine remaining charge (current coulomb count). This maybe referred to as the state of charge (“SOC”). The robot determines whenrecharging is needed by comparing the SOC to a predetermined thresholdlevel, as described above.

The amount of charge used by the electric motors 810 and 812 andcontroller board 802 is significantly greater than the amount of chargedused to power the other components of the robot and thus may be used asthe overall current usage for the robot or if greater precision isdesired the current usage by the components other than the electricmotors 810 and 812 may be measured and considered in the coulomb count.

Operation of the software and protocols for charging are described inthe following section.

Robot Charging Software/Protocols

The batteries used in the robots described herein will typically have arelatively flat current discharge vs. voltage curve. And, they may behighly temperature dependent. These characteristics are evidenced by thefive curves shown for −20 C, 0 C, 23 C, 45 C, and 60 C illustrated inthe graph of FIG. 21. The graph depicts the curves for one LiFePO4(Lithium Iron Phosphate) battery having a 13.5V open-circuit voltagedischarged by 16 A. As the battery is discharged, the battery voltagedeclines from approximately 13.5V to approximately 10V. On the rightside of the graph, where battery has discharged a certain amount ofcapacity, the curves intersect the “X” axis, indicating 10V of potentialremaining in the battery. The 23 C and 45 C curves dischargeapproximately 16 A. With the 60 C curve, the battery management system'sover temperature protection activates and shuts down the battery afterabout 14.4 A have been discharged. At colder temperatures, namely, at 0C and −20 C, all available energy cannot be removed from the battery andafter discharging only about 14.4 A and 12.24 A, respectively, thebattery stops functioning. As shown, the battery voltage remains fairlyconstant over a wide range of charge levels.

For example, at 23 C from just below fully charged to about a pointwhere 14.4 A have been discharged the voltage varies only from 12.8V tojust below 12.5V. As a result, the SOC cannot be reliably estimated fromvoltage alone. Thus, a reliable and accurate two-part algorithm may beused for the SOC estimation with the robot battery packs describedherein.

The first aspect of the SOC algorithm utilizes a coulomb-counting (1coulomb=lampere*1 second) approach where current is accurately measuredduring both charging (by charging station 500 using current sensor 650,FIG. 19) and discharging (by the robot using current sensor 806, FIG.20) of the batteries and integrating over time the measured current todetermine total number of coulombs charged or discharged over a periodof time. While charging, the integrated charge level is maintained innon-volatile storage on controller board 572 to maintain tracking overpower-down periods. Also, while charging, the charge level isperiodically communicated to the robot and saved in memory on, e.g.,motor controller 802. When the robot leaves the charging station (i.e.the robot is undocked), the amount of current being discharged ismonitored and from the original charge level, the current SOC can bedetermined.

Using coulomb counting alone, however, results tend to drift due tomeasurement error integrated over time To overcome this, there is asecond aspect of the algorithm which uses full-charge/full-dischargethresholds. In other words, voltage level thresholds may be used by therobot to reliably detect full discharge and full charge states and thesestates can then be used for integrator reset to correct for drift ofestimated charge. The robot will be responsible for maintaining the SOCestimate, for discharge coulomb-counting, and for detecting full chargeand full discharge states. The charger will be responsible forcoulomb-counting during charging.

Referring again to FIG. 21, as the battery gets charged (moving right toleft along the graph for a given temperature), eventually the voltagewill rise to a predetermined upper voltage threshold, which in this casemay be approximately 14.3V (per battery). The robot uses this upperthreshold as a way of determining that the battery is fully charged. Itknows its SOC by determining the most recently stored coulomb count inmemory when the threshold voltage level is reached. The robot may thendepart the charging station and begin the coulomb counting process todetermine the amount of charge being used.

While the robot described herein uses a process to maintain an accurateestimate of battery pack capacity and the intention is that it willreach a charging station autonomously prior to the battery reaching afully discharged state, the system is designed to recover robots whichhave reached such a fully discharged battery state before docking at acharging station. As the battery is discharged (moving left to rightalong the graph), if the voltage drops to a lower threshold voltagelevel, e.g. 9 V (per battery), this lower threshold may be used toindicate that the battery is fully discharged. At this lower thresholdvoltage level, the robot is automatically powered down to avoid damagingthe battery. A manual restart of the robot would be needed after therobot is moved to a docking station and provided with a recovery charge,as described below. When the battery packs drop to a certain low voltagelevel (e.g. 8V per battery) they will typically trigger an internalprotective shut down and the battery will no longer take a charge. Toprevent this terminal condition from being triggered, the robot may beconfigured to power down at the predetermined low voltage threshold(e.g. 9V each battery), which is above the terminal voltage level.

Note that the full discharge condition may only occur occasionally. Thisis because the robot may be programmed to return to a charging stationfor recharging at a predetermined SOC, which would be known to be abovethe full discharge level. In other words, there typically will be set aSOC level above the point of a full discharge (e.g. 10-20% above fulldischarge level). When such a level is reached, the robot will travel toa charging station for recharging. Once the robot knows that it must berecharged, it may determine the nearest available charging station.Robots operating in the space and/or the warehouse management systemwill coordinate at a higher level to ensure that only one robot willattempt to dock with a particular charging station at a time. Asdescribed above, each charging station will have a unique identifier anda pose associated with it. The robot will navigate to the pose of theselected charging station and begin the docking process, both processesare described above in detail.

The robot may use the number of full charges/discharges to provide thesystem operator with an end-of-life warning for the packs. Thesestatistics are written to nonvolatile storage (flash) on power-down andread from nonvolatile storage (flash) on power-up. For example, when acertain number of full charge and/or discharge states are reached, therobot may indicate that factory servicing of the battery is required.Also the SOC at given voltage levels may be monitored to determine ifthe battery is no longer sufficiently holding a charge, in which casethe robot may also indicate that factory servicing of the battery isrequired.

When a robot arrives at a charging station and is docked, communicationswill be established between the robot and the charging station by theIrDA boards 574 and 816, respectively, and the charging process willbegin. Successful docking may be confirmed and indicated when thebattery voltage is sensed by the charging station controller 572, FIG.19, to be greater than a threshold value (with hysteresis) across theelectrical charging assembly 200. With Battery pack 800, FIG. 20,described herein the threshold voltage level may be 18V with 1Vhysteresis (2 batteries*9V). The detected voltage level may becommunicated to the robot via IrDA communications and the robot mayconfirm that the voltage readings received are in agreement with therobot internal voltage measurement within some tolerance level.

After communications are established and the threshold voltage level isconfirmed, the charging process will not be enabled unless a shortcircuit condition is not detected and the battery temperature (detectedby the robot and supplied to the charging station via IrDA) is within anacceptable range. For battery pack 800, the temperature range may beabove 0 C and below 45 C degrees. An indication of battery type on therobot (either robot type or battery type or some other indicator) may becommunicated via IrDA communications to the charging station and fromthe battery type, a specific charging profile may be selected. At thestart of charging, coulomb counting is initialized and the chargingprocess begins according to the selected charging profile.

The charging process according to a charging profile for one particularbattery type is described with regard to Table 1 below and flow chart850, FIG. 22. Also, depicted in the Table 1 are the parameters for ageneric battery recovery for a fully discharged battery. As indicated inthe Table 1, the charging profile for the given battery has differentparameters used in different circumstances. For normal or fast chargingthere is a set of charging parameters which differ from the parametersfor extreme temperatures (hot or cold outside of specific ranges).

The recovery mode parameters are used when a robot is manually dockedafter being fully discharged and a manual recovery switch has beenpressed to start charging. In other words, these parameters would beused to initially charge any type of robot battery sufficiently untilthe robot can be restarted and IrDA communications can bere-established.

In the case of a full discharge battery recovery, since the robot willno longer turn on, IrDA communications cannot be established and thecharging station will not know the battery type of the robot. Once anoperator has manually docked the robot to the charging station, a manualstart pushbutton on the charging station will be pressed and held. Ageneric initial charging profile is instituted by outputting a lowcharge current until a threshold battery voltage is reached, at whichtime an indication is given to the operator to turn on the robot. Onceturned on, the IrDA communications are established and the normalautonomous charging process is initiated.

TABLE 1 Termination Voltage for Post- Current for Charge Float ChargingPrecharge Termination Charge Current Charge Voltage Constant Phase toPower Profile Current/ Voltage/ for Constant for Constant Voltage RobotUntil Name Recovery Recovery Current Phase Voltage Phase Phase UndockedFast 5.0 A 25.50 V 34.0 A 28.6 V 1.25 A 27.2 V Extreme 3.0 A 25.50 V20.0 A 28.6 V 1.25 A 27.2 V Temperature Recovery 2.0 A 25.50 V 20.0 A28.6 V 0.50 A  0.0 V

Referring to flow chart 850, FIG. 22, at step 851 the charger determinesif a robot is docked by checking for a voltage sensed at the charger. Ifa robot is docked, at step 852, the charging station determines if IrDAcommunications with a docked robot have been established. If IrDAcommunications have not been established, at step 854, it is determinedif the manual start button has been pressed to initiate a manualcharging process of a robot with a fully discharged battery. If themanual start button has been pressed, the recovery charge profile isobtained and the system proceeds to step 862. If in step 852,communications are established with the robot, the system proceeds tostep 858 where the battery type or robot type and battery condition(i.e. temperature) of the docked robot is communicated to the chargingstation. From the battery/robot type and battery condition, theparticular charging profile for the battery is recovered from memory instep 860 and the system then proceeds to step 862.

At step 862 it is determined if the battery voltage is less than thethreshold voltage, which in the charging profiles (fast, extremetemperature, and recovery) of Table 1 is 25.5V. If the battery voltageis not below the threshold voltage the system proceeds to step 868. Ifthe voltage is below the threshold voltage, at step 864, pre-charging isundertaken at a constant current as set forth in Table 1. The particularpre-charge current will be dependent upon the charging profile beingused. Thus, for the example in Table 1, the fast charging thepre-charging current is 5.0 A, for extreme temperature the pre-chargingcurrent is 3.0 A, and for recovery the pre-charging current is 2.0 A.While pre-charging, the voltage at the charger terminal is being checkedat step 866 to determine if the threshold voltage has been reached. Ifit has been reached the system proceeds to step 868 and if notpre-charging continues until the threshold voltage is reached.

At step 868, the main charging process begins with a constant currentcharging stage using the current selected from the particular chargingprofile being used. In the example of Table 1, for fast charging, thecharging current is set at 34 A, while for extreme temperature chargingas well as recovery charging, the charging current is set at 20 A. Ineach case, this continues until at step 870 a predetermined voltagelevel is attained. In the example of Table 1, the predetermined voltagelevel for fast, extreme temperature and recovery charging is 28.6V. Oncethis voltage level is reached, at step 872, a fixed voltage chargingstage is undertaken, with the charging voltage maintained at 28.6Vcharging continues until a termination current is reached, as determinedby step 874. The termination current for the fast and extremetemperature charging profiles in Table 1 is 1.25 A and for the recoverycharging profile it is 0.5 A. Such a low level of charge current beingsupplied at the constant voltage is indicative that the robot is nearlyat full charge, so the charger station terminates the main chargingprocess.

The system proceeds to step 876 where the SOC is communicated to therobot. While not specifically shown in flow chart 850, during thepre-charging and main charging processes, the SOC may be communicated tothe robot regularly, e.g. once per second. At this point the robot mayundock from the charging station, however, that is under the control ofthe robot. As described above, during charging, the battery voltage ismonitored and it will eventually rise to a predetermined upper voltagethreshold, e.g. 14.3V (per battery). The robot uses this upper thresholdas a way of determining when the battery is fully charged. It uses theSOC most recently stored in memory when the upper voltage threshold isreached as its initial coulomb count if it decides to undock at thatpoint. In certain situations, the robot may remain docked event thoughit is fully charged. One reason for the robot to remain at the chargingstation may be due to receiving a command from the warehouse managementsystem to remain at the charging station if it is not needed on thefloor. If the robot were to remain at the charging station after themain charging process is completed it would lose its charge over time.Therefore, a float charge process may be instituted to maintain thecharge of the robot.

At step 878, it is determined if the charging profile includes a floatcharge phase. If it does not, the system proceeds to step 880, where itis determined if the robot has undocked. If it has not, the systemcycles back to step 880 until the robot has undocked and then the systemproceeds to step 881 where charging by the charging station isterminated. The system then proceeds to step 851 and waits for the nextrobot to dock for charging. When the robot departs the charging stationit begins the coulomb counting process to determine the amount of chargebeing used.

If at step 878, it is determined that the charging profile includes afloat charge phase, at step 882 a float phase is instituted. In thefloat phase, the charging voltage of the charging station is fixed atfloat phase voltage level while a “trickle charge” is input the robot.In the example of Table 1, for the fast and extreme temperatureprofiles, the float phase voltage may be 27.7V. The resulting tricklecharge may be approximately 0.2 A. During the float phase, the chargeris supplying a standby current which is consumed by the robot (assumingthe robot is turned on). Robot standby current consumption isapproximately 0.2 A (200 mA), but is not regulated by the charger. Thiscontinues until the robot undocks as determined at step 884. When therobot undocks the system proceeds to step 881 where charging by thecharging station is terminated. The system then proceeds to step 851 andwaits for the next robot to dock for charging. And, when the robotdeparts the charging station it begins the coulomb counting process todetermine the amount of charge being used.

Although not depicted in flow chart 850, there are several events thatcan occur during the charging process that require the process to beterminated. This includes a short circuit condition which can bedetected by estimating load resistance based on the ratio of currentover voltage. If this is below a threshold value, e.g. 50M Ohm, thecharging station may determine that a short circuit has been detectedand terminate the charging process. Additionally, if an open orresistive circuit (greater that a threshold, e.g. 1 Ohm) is detected thecharging process may also be terminated to prevent overheating. If IrDAcommunications are lost or other important conditions are detected thecharging process may be terminated. As described above, the integratedcharge level is maintained in non-volatile storage on controller board572 to ensure accurate charge tracking during power-down periods.

The higher level operation of charging station 500 is depicted in statemachine 900 of FIG. 23. The charging station 500 is powered up andinitialized at state 902. Once initialization is complete, the chargingstation enters an idle mode at state 904 and waits for either a batteryto be detected (robot ready for automatic charging) or a manual overrideinput to be detected (button pressed by operator to enter the manualcharging mode for a robot with a “dead” battery). If a battery isdetected the system proceeds to state 906 where communications betweenthe robot and the charging station are established. If a manual overrideinput is detected the system proceeds to start recovery state 908.

In the automatic charge process, if communications with the robot arenot established at state 906, a communication error is determined atstate 910 and the system returns to the idle state 904. Ifcommunications are established at state 906 the charging process beginsat state 912 as described above. At the completion of charging, if therobot request a charge cycle log (CCLOG), at step 914, the chargingstation sends to the robot the CCLOG and terminates the charging processat state 916. If the robot does not request the CCLOG, the system simplyproceeds from charging state 912 to the done state 916. In either case,the robot then returns to the idle state 904.

If instead, the manual override input is detected, at state 908 themanual recovery process begins. If a battery is not detected or batteryis in protective shutdown mode, the system enters the recovery failedstate 918 and then returns to the idle state 904. If in start recoverystate 908 the battery is detected and the battery is not in protectiveshutdown, the recovery process as described above is undertaken in state920. When the recovery process is completed at state 922, the systemproceeds to establish communications with the robot at state 906 andundertake the automatic charging process.

While not shown in state machine 900, there are several events that canoccur during the charging process that require the process to beterminated, for example, a short circuit or open circuit, or if therobot leaves the charging station before charging is complete.

While the foregoing description of the invention enables one of ordinaryskill to make and use what is considered presently to be the best modethereof, those of ordinary skill will understand and appreciate theexistence of variations, combinations, and equivalents of the specificembodiments and examples herein. The above-described embodiments of thepresent invention are intended to be examples only. Alterations,modifications and variations may be effected to the particularembodiments by those of skill in the art without departing from thescope of the invention, which is defined solely by the claims appendedhereto. The invention is therefore not limited by the above describedembodiments and examples.

Having described the invention, and a preferred embodiment thereof, whatis claimed as new and secured by letters patent is:

I/We claim:
 1. An electrical charging station for charging an autonomousrobot having a battery, comprising: A first charging member on theelectrical charging station configured to receive a second chargingmember on the autonomous robot when the autonomous robot is docked withthe charging station for charging; A communications device configured toreceive from the autonomous robot an identifier indicative of a type ofbattery on the autonomous robot; and A power supply, electricallyconnected to the first charging member, configured to charge theautonomous robot according to a charging profile; Wherein the chargingprofile is selected based at least in part on the identifier receivedfrom the autonomous robot.
 2. The electrical charging station of claim 1wherein the identifier comprises one or more of a battery type, anautonomous robot type, or battery condition.
 3. The electrical chargingstation of claim 2 wherein the battery condition includes a batterytemperature and wherein for a certain battery type the charging profilefor a normal battery temperature range is different than the chargingprofile for either a battery temperature above the normal temperaturerange or below the normal temperature range.
 4. The electrical chargingstation of claim 2 wherein the charging station includes a memory forstoring a plurality of charging profiles, at least one of whichcorresponds to the identifier.
 5. The electrical charging station ofclaim 4 wherein the communications device includes a transceiver forcommunicating with a corresponding transceiver on the autonomous robot.6. The electrical charging station of claim 5 wherein the transceiver ofthe charging station and the corresponding transceiver on the autonomousrobot are optical transceivers and communicate using an IrDAcommunications protocol.
 7. The electrical charging station of claim 6further including a current sensor configured to sense a current outputfrom the power supply to the autonomous robot and a voltage sensorconfigured to sense a voltage across the first charging member appliedby the power supply.
 8. The electrical charging station of claim 7further including a processor configured to control the power supply tocharge the autonomous robot according to the charging profile; whereinthe charging profile includes a constant current portion and a constantvoltage portion.
 9. The electrical charging station of claim 8 whereinthe processor is configured to charge the robot in the constant currentcharging portion of the charging profile using a constant current untila predetermined voltage level is reached and to then charge the robot inthe constant voltage portion of the charging profile using a constantvoltage.
 10. The electrical charging station of claim 9 wherein duringthe constant voltage charging portion of the charging profile theprocessor is configured to provide the SOC to the robot and terminatecharging when a SOC request from the robot has been received indicatingan upper battery voltage threshold has been reached or when apredetermined current level is being output by the power supply, in bothcases indicating a fully charged battery.
 11. The electrical chargingstation of claim 10 wherein the processor is configured to control thepower supply after the robot is fully charged but before the robot hasundocked from the charging station to charge the robot using a floatcharging profile which provides a limited charge level to the robot bymaintaining a constant voltage level until the robot is undocked. 12.The electrical charging station of claim 10 wherein the processor isconfigured to charge the robot in a dead battery state using a recoveryprofile having a constant current portion and a constant voltageportion, and wherein the processor is further configured to prompt auser to start the robot upon completion of the recovery charging profileso that communication between the robot and the charging station can beestablished to complete robot charging using a charging profile selectedbased at least in part on the identifier received from the autonomousrobot.
 13. A method for charging an autonomous robot having a battery,comprising: Docking an autonomous robot by mating a first chargingmember on an electrical charging station with a second charging memberon the autonomous robot; Receiving a communication from the autonomousrobot including an identifier indicative of a type of battery on theautonomous robot; and Charging, using a power supply, the autonomousrobot according to a charging profile; Wherein the charging profile isselected based at least in part on the identifier received from theautonomous robot.
 14. The method of claim 13 wherein the identifiercomprises one or more of a battery type, an autonomous robot type, orbattery condition.
 15. The method of claim 14 wherein the batterycondition includes a battery temperature and wherein for a certainbattery type the charging profile for a normal battery temperature rangeis different than the charging profile for either a battery temperatureabove the normal temperature range or below the normal temperaturerange.
 16. The method of claim 14 wherein the method further includesstoring in a memory in the charging station a plurality of chargingprofiles, at least one of which corresponds to the identifier.
 17. Themethod of claim 16 wherein the receiving step includes communicatingwith optical transceivers one on each of the autonomous robot and on thecharging station using an IrDA communications protocol.
 18. The methodof claim 17 further including sensing a current output from the powersupply to the autonomous robot using a current sensor and sensing avoltage across the first charging member applied by the power supplyusing a voltage sensor.
 19. The method of claim 18 further includingcontrolling the power supply to charge the autonomous robot according tothe charging profile; wherein the charging profile includes a constantcurrent portion and a constant voltage portion.
 20. The method of claim19 further including charging the robot in the constant current chargingportion of the charging profile using a constant current until apredetermined voltage level is reached and charging the robot in theconstant voltage portion of the charging profile using a constantvoltage until a predetermined current level is reached.
 21. The methodof claim 20 wherein during the constant voltage charging portion of thecharging profile providing the SOC to the robot and terminating chargingwhen a SOC request from the robot has been received indicating an upperbattery voltage threshold has been reached or when a predeterminedcurrent level is being output by the power supply, in both casesindicating a fully charged battery.
 22. The method of claim 21 furtherincluding controlling the power supply after the robot is fully chargedbut before the robot has undocked from the charging station to chargethe robot using a float charging profile which provides a limited chargelevel to the robot by maintaining a constant voltage level until therobot is undocked.
 23. The method of claim 21 further including chargingthe robot in a dead battery state using a recovery profile having aconstant current portion and a constant voltage portion, and prompting auser to start the robot upon completion of the recovery charging profileso that communication between the robot and the charging station can beestablished to complete robot charging using a charging profile selectedbased at least in part on the identifier received from the autonomousrobot.